It is known in the field of internal combustion engineering that there are significant advantages in operating an internal combustion engine with "lean" fuel-to-air ratios. Such operation lowers the combustion temperature and tends to reduce objectionable nitrogen oxide and carbon monoxide emissions. Additionally, such operation improves the completeness of combustion and may actually also improve the overall engine efficiency as contrasted with the use of more conventional fuel-air mixture ratios. In spite of the recognized advantages in the use of such "lean" mixtures, several important problems have obviated the general adoption of such operation.
One practical difficulty is that the desired fuel-to-air ratios are near the limit of ignitability by a conventional spark system. Furthermore, poor distribution of the fuel charge may be responsible for one or more of the engine cylinders not being ignited. As a consequence, excessive quantitives of hydrocarbon fuel are dumped or discharged into the exhaust gases. It has been found that improved sparking does little to alleviate the situation. Some improvement is achieved through carburetion and modified manifolding, but not much. Better distribution of fuels through the use of injection systems has provided definite improvements, but at markedly increased cost and mechanical complexity. Moreover, none of these measures helps significantly when the fuel-to-air ratio is drastically reduced.
Another approach toward reaching a solution has been the utilization of stratified charge engines where injection of the fuel into the cylinder is used to provide a region of reasonably rich mixture in a charge of lean-to-average fuel-to-air ratio. Such systems have experienced some success but again at the expense of mechanical complexity, and even then with difficulty over a broad range of operating conditions. The fuel injection systems offer an advantage over a diesel engine only in the fact that the spark ignition makes possible the control of ignition lag, and thereby also makes possible multiple fuel operation.
Still another approach toward dealing with the problem has been the introduction of the CVCC engine, and a family of new derivative engines. In this system, a rich fuel-to-air mixture is held in a separate chamber provided with separate valving and is fired by a spark. The ignited fuel then rushes out of the separate chamber into the main chamber to accomplish ignition of the remaining, lean charge by turbulent mixing, among other effects.
While each of the above prior art approaches toward resolving the problems posed has contributed some insight, each offers only a significantly limited solution to the recognized problems. It is, therefore, the aim of the present invention to provide a simple mechanical system which incorporates all of the advantages of each of the prior art approaches without the requirement of charge stratification and without the requirement of special manifolding and injectors.